You can export the data by loading the .psdata file back into PicoScope 6 and then clicking File -> Save As... and changing the save as type to Matlab 4 files (*.mat).

Please note that if your file contains more than 100MS per channel, then the file will not load into MATLAB (this is a limitation of the .mat v4 format). If this is the case please e-mail support@picotech.com attaching the psdata file if it is a small file or with a link to where to download it from.